Acupoints, which constitute an important part of the Chinese meridian theories, refer to specific positions on the superficial meridians (i.e., pathways distributed in the human body to facilitate the circulation of life force, or qi, between body organs) that serve as confluences, relay stations, and entrances/exits of qi. When a person falls ill, the corresponding acupoints tend to have such pathological reactions as pain (when pressed), soreness, numbness, nodule formation, and/or swelling. A doctor, therefore, can diagnose a patient's disease according to the pathological reaction(s) taking place and may also treat the patient by stimulating the corresponding acupoints.
Conventionally, acupoints are stimulated by acupuncture or tui na. With the advancement of science and medicine, however, electrotherapy has been a major means of acupoint stimulation, given the fact that acupoints have proved to have low electrical resistance and high conductivity. For example, Dr. Richard Croon of Germany found a relationship between acupoints and the low-resistance points on the skin; Dr. Reinhold Voll, also of Germany, verified the existence of several low-resistance superficial channels in the human body that resemble the meridians in traditional Chinese medicine; and Dr. Yoshio Nakatani of Japan found a relationship between acupoints and ryodoraku, a specific form of acupuncture developed by the Japanese. Electrotherapy is a physical treatment involving electrical stimulation and is conducted as follows. To start with, electrode pads are attached to a patient's skin. Then, a series of current signals generated by an electrotherapeutic signal generator are sent through the electrode pads to the muscle groups under the skin to induce rhythmic yet involuntary partial contraction and relaxation of the muscle groups, thus stimulating the intended acupoints in a way similar to acupuncture.
Electrotherapy is non-invasive, non-pharmacological, and hence an ideal treatment for personal health maintenance at home. Transcutaneous electrical nerve stimulation (TENS) and electrical muscle stimulation (EMS), for instance, are two common methods of electrotherapy nowadays. TENS, which uses low-frequency pulse current to control pain, is based on the “gate control theory”, according to which epidermal nerves (e.g., the Aβ nerve fibers) can be stimulated with weak low-frequency current to generate signals that turn off the “gate” of the corresponding sensory nerves (e.g., the Aδ nerve fibers and the C nerve fibers), thereby stopping the conduction of pain and producing a painkilling effect. EMS, on the other hand, causes muscle contraction and relaxation by stimulating the corresponding motor nerves so that passive physical exercise is carried out for the intended treatment or training. By adjusting the current frequency of the electrotherapeutic signals generated by a TENS or EMS device, therefore, simulated acupuncture can be achieved to stimulate the target acupoints.
However, the inventor of the present invention has found that most of the aforesaid electrotherapeutic instruments use electrode pads as the elements required for transmitting electrotherapeutic signals, and that each time electrotherapy is performed, each target acupoint has to be attached with one electrode pad because the electrode pads generally have a small surface area and must be adhesively and securely attached to all the intended acupoints respectively in order to produce the expected electrotherapeutic effect. Accordingly, multiple electrode pads are needed when it is desired to conduct electrotherapy on several acupoints at the same time, and the electrode pads must be respectively and adhesively attached to the acupoints before the electrotherapy begins so that all the acupoints can receive the therapy at once. It would be very inconvenient if electrotherapy is applied to a plurality of acupoints by turns. The sole of a human foot, for example, has many acupoints and includes reflex areas for almost all the organs in the body. It is common practice, therefore, to manually massage the acupoints in the soles, with a view to stimulating the reflex areas, promoting blood circulation through the body organs, discharging the wastes or toxins in the organs, and thereby enhancing metabolism. But if it is desired to stimulate the acupoints in the soles by electrotherapy instead of manual massage, the electrode pads cause problems. Since each electrode pad covers only a small area, and different parts of a human sole vary greatly in curvature, a large number of electrode pads must be used; nevertheless, it is difficult to firmly attach the electrode pads to all the intended acupoints respectively.
As a solution, shoe soles adapted for electrotherapy were developed, allowing a user's entire foot to stamp on such a sole. These soles are typically provided therein with additional electronic elements (e.g., conductive wires) or are coated with a conductive material such that the manufacturing process is exceedingly complicated. Moreover, when stamped on repeatedly for a long time, the electronic elements are prone to damage (e.g., the conductive wires may be broken), or the conductive material may peel off. In either case, the sole in question will lose its electrotherapeutic effect. Hence, the issue to be addressed by the present invention is to design a novel sole structure that not only has a simple production process, but also is structurally simple to ensure a lasting electrotherapeutic effect during long-term use.